Wafer debonding using long-wavelength infrared radiation ablation

ABSTRACT

Structures and methods are provided for temporarily bonding handler wafers to device wafers using bonding structures that include one or more releasable layers that absorb long-wavelength infrared radiation to achieve wafer debonding by infrared radiation ablation.

TECHNICAL FIELD

The field generally relates to wafer handling techniques and, inparticular, to structures and methods for temporarily bonding handlerwafers to device wafers using bonding structures that include one ormore releasable layers that absorb infrared radiation to achieve waferdebonding by infrared radiation ablation.

BACKGROUND

In the field of semiconductor wafer processing, increasing demands forlarge-scale integration, high density silicon packages has resulted inmaking semiconductor dies very thin. For example, for some applications,silicon (Si) wafers are backside grinded and polished down to athickness of 50 μm or thinner. Although single crystal Si has very highmechanical strength, Si wafers and/or chips can become fragile as theyare thinned. Defects can also be introduced by processing steps such asthrough-silicon via (TSV) processing, polishing, and dicing, whichfurther reduces the mechanical strength of a thinned wafer or chip.Therefore, handling thinned Si wafers presents a significant challengeto most automation equipment.

In order to facilitate the processing of a device wafer, a mechanicalhandler wafer (or carrier wafer) is usually attached to the device waferto enhance the mechanical integrity of the device wafer duringprocessing. When processing of the device wafer is complete, the handlerwafer needs to be released from the device wafer. The most commonapproach to handling a device wafer is to laminate the handler waferwith the device wafer using specially developed adhesives. Depending onfactors such as the processing steps, the product requirements, and thetype of the adhesive, various techniques have been used or proposed todebond or separate a thinned device wafer from a mechanical handlerwafer, including thermal release, chemical dissolving, and laserablation techniques.

A typical laser-assisted debonding process uses a polymeric adhesive(which is capable of sufficient absorption of energy in the UV (ultraviolet) spectrum) to bond a device wafer to a UV transparent glasshandler wafer. A laser ablation process is performed to ablate thepolymeric adhesive and achieve debonding between the glass handler waferand the device wafer. The use of a glass handler in the UV laserablation process has several drawback including poor thermalconductivity, incompatibility with certain semiconductor processingequipment, as well as high cost. Although the use of Si wafer handlerscan potentially overcome these drawbacks, silicon is not transparent toUV spectrum and therefore is not compatible with previously developed UVlaser release technology.

SUMMARY

In general, embodiments of the invention include structures and methodsfor temporarily bonding handler wafers to device wafers using bondingstructures which include one or more releasable layers that absorbinfrared radiation to achieve wafer debonding by infrared radiationablation.

In one embodiment of the invention, a stack structure includes a devicewafer, a handler wafer, and a bonding structure disposed between thedevice wafer and the handler wafer to bond the device and handler waferstogether. The bonding structure includes an adhesive layer, and ametallic layer. The metallic layer serves as a releasable layer of thebonding structure by infrared ablation of the metallic layer.

In another embodiment of the invention, a stack structure includes adevice wafer, a handler wafer, and a bonding structure disposed betweenthe device wafer and the handler wafer to bond the device and handlerwafers together. The bonding structure comprises an adhesive layerhaving infrared energy absorbing nanoparticles. The adhesive layerserves as a releasable layer by infrared ablation of the adhesive layer.

In another embodiment of the invention, a method is provided forhandling a device wafer. The method includes providing a stack structurehaving a device wafer, a handler wafer, and a bonding structure disposedbetween the device wafer and handler wafer, and irradiating the bondingstructure with long-wavelength infrared energy to ablate the bondingstructure.

These and other embodiments of the invention will be described or becomeapparent from the following detailed description of embodiments, whichis to be read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is flow diagram of a method for processing and handling asemiconductor wafer according to an embodiment of the invention.

FIG. 2 schematically depicts a stack structure comprising a bondingstructure for temporarily bonding a device wafer to a handler wafer,according to an embodiment of the invention.

FIG. 3 schematically depicts a stack structure comprising a bondingstructure for temporarily bonding a device wafer to a handler wafer,according to another embodiment of the invention.

FIG. 4 schematically depicts a stack structure comprising a bondingstructure for temporarily bonding a device wafer to a handler wafer,according to another embodiment of the invention.

FIG. 5 schematically depicts a stack structure comprising a bondingstructure for temporarily bonding a device wafer to a handler wafer,according to another embodiment of the invention.

FIG. 6 schematically depicts a stack structure comprising a bondingstructure for temporarily bonding a device wafer to a handler wafer,according to another embodiment of the invention.

FIG. 7 schematically depicts a stack structure comprising a bondingstructure for temporarily bonding a device wafer to a handler wafer,according to another embodiment of the invention.

FIG. 8 schematically depicts a stack structure comprising a bondingstructure for temporarily bonding a device wafer to a handler wafer,according to another embodiment of the invention.

FIG. 9 schematically depicts a stack structure comprising a bondingstructure for temporarily bonding a device wafer to a handler wafer,according to another embodiment of the invention.

FIGS. 10A, 10B and 10C schematically depict an apparatus to perform adebonding process to separate a device wafer and handler wafer,according to an embodiment of the invention.

DETAILED DESCRIPTION

Embodiments of the invention will now be discussed in further detailwith regard to structures and methods for temporarily bonding siliconhandler wafers to device wafers using bonding structures that includeone or more releasable layers that absorb infrared radiation to achievewafer debonding by infrared radiation ablation. For example, FIG. 1 isflow diagram that illustrates a method for processing and handling asemiconductor wafer according to an embodiment of the invention.Referring to FIG. 1, the method includes performing a wafer bondingprocess by bonding a handler wafer (or handler substrate) to a devicewafer (or chip) using a bonding structure that comprises an adhesivelayer and a thin metallic layer (step 10). In one embodiment of theinvention, the handler wafer is a Si handler wafer (or substrate) whichis bonded to a Si device wafer, as the use of a mechanical Si handlerwafer enables compatibility with standard CMOS silicon wafer processingtechnologies. In other embodiments of the invention, the handler wafercan be formed of other suitable materials that are transparent orsemi-transparent (e.g., 50% transparent) to certain wavelength in theinfrared (IR) spectrums that are used for IR laser ablation.

Moreover, bonding structures according to embodiments of the inventionutilize one or more adhesive layers and thin metallic layers that serveas releasable layers that are ablated using IR radiation to debond thedevice and handler wafers. In particular, in one embodiment, a bondingstructure comprises one or more thin metallic layers that are configuredto strongly absorb IR energy emitted from a pulsed IR laser and improvethe ablation efficiency, and reduce an ablation energy threshold forbonding structures. Indeed, with these bonding structures, anultra-short pulse of IR energy from the IR laser can be readily absorbedby the thin metallic layers (constrained in a very shallow depth withinthe bonding structure) to thereby quickly and efficiently vaporize atleast a portion of the thin metallic layer and at least a portion of theadhesive layer at an interface between the adhesive layer and the thinmetallic layer, and release the device wafer from the handler wafer.Various bonding structures according to alternative embodiments of theinvention will be described in further detail below with reference toFIGS. 2-9.

Referring again to FIG. 1, once the wafer bonding process is complete,standard wafer processing steps can be performed with the handler waferattached to the device wafer (step 11). For instance, in one embodimentof the invention, the handler wafer is bonded to a BEOL(back-end-of-line) structure formed on an active surface of the devicewafer. In this instance, standard wafer processing steps such asgrinding/polishing the backside (inactive) surface of the device waferto thin the device wafer can be performed. Other wafer processing stepsinclude forming through-silicon-vias through the backside of the devicewafer to the integrated circuits formed on the active side of the devicewafer. In other embodiments, the device wafer may be subject to a waferdicing process with the handler wafer attached such that an individualdie, or multiple dies, can be held by the temporary handler wafer fordie assembly or other processes where the dies are assembled to asubstrate or another full thickness die, and then released in subsequentoperations such as post assembly or post underfill. During theseprocessing steps, the handler wafer will impart some structural strengthand stability to the device wafer, as is readily understood by those ofordinary skill in the art.

A next step in the illustrative process of FIG. 1 involves performing alaser ablation wafer debonding process to release the device wafer fromthe handler wafer (step 12). In one embodiment, this process involvesirradiating the bonding structure through the handler wafer usinglong-wavelength IR energy to laser ablate the bonding structure andrelease the device wafer. More specifically, in one embodiment, theprocess involves directing a pulsed IR laser beam at the handler wafer,and scanning the pulsed IR laser beam across at least a portion of thestack structure to laser ablate at least a portion of the bondingstructure. As noted above, ablation of the bonding structure comprisevaporizing at least a portion of the thin metallic layer and/orvaporizing at least a portion of the thin metallic layer and adhesivelayer at an interface between the adhesive layer and the thin metalliclayer, which enables release of the device wafer from the handler wafer.Various embodiments of an IR laser ablation process will be described infurther detail below with reference to FIGS. 2-10.

Once the IR laser ablation process is complete and the device wafer isreleased from the handler wafer, a post debonding cleaning process canbe performed to remove any remaining adhesive material or other residue(resulting from the ablation of the bonding structure) from the devicewafer (step 13). For example, cleaning process can be implemented usinga chemical cleaning process to remove any polymer based adhesivematerial, or other known cleaning methods to remove residue of theablated bonding structure.

FIG. 2 schematically depicts a stack structure comprising a bondingstructure for temporarily bonding a device wafer to a handler wafer,according to an embodiment of the invention. More specifically, FIG. 2is a schematic side view of a stack structure 20 comprising a silicondevice wafer 21, a silicon handler wafer 22, and a bonding structure 23.The bonding structure 23 comprises an adhesive layer 24 and a thinmetallic layer 25. FIG. 2 further illustrates an IR laser 14 that emitsan IR laser beam at the handler wafer 22 to irradiate a portion of thebonding structure 23 resulting in a laser-ablated region 16.

In one embodiment of the invention, IR laser 14 emits a pulsed infraredlaser beam to laser ablate the bonding structure 23, wherein the IRlaser 14 emits a long wavelength infrared laser beam with an outputwavelength that is greater than about 5 μm. In one alternativeembodiment, the IR laser 14 is a far infrared (FIR) laser having anoutput wavelength in a far IR portion of the electromagnetic spectrumbetween about 5 μm and 30 μm. The silicon handler wafer 22 isapproximately 50% transparent at these frequencies so that the laserbeam will penetrate the handler wafer 22 and irradiate the bondingstructure 23.

In one embodiment, the adhesive layer 24 may be formed of any suitablepolymer adhesive material that may or may not be capable of sufficientlyabsorbing the IR energy output from the IR laser 14. Irrespective of theIR absorption ability of the adhesive layer 24, in one embodiment of theinvention, the thin metallic layer 25 is configured (in materialcomposition and thickness) to intensely absorb the IR energy and serveas a primary releasable layer of the bonding structure 23, which isablated by the IR laser energy. The thin metallic layer 25 improves thelaser ablation efficiency and thus, reduces the ablation threshold ofthe bonding structure 23 (as compared to a bonding structure that usesan adhesive layer alone). In one embodiment of the invention, thebonding structure 23 is irradiated with infrared energy sufficient tofully vaporize (ablate) at least a portion of the thin metallic layer 25that is exposed to the IR energy.

Moreover, in an alternate embodiment of the invention, the bondingstructure 23 is irradiated with infrared energy sufficient to fullyvaporize (ablate) at least a portion of the thin metallic layer 25 thatis exposed to the IR energy, as well as vaporize, denature, carbonize,or otherwise ablate and at least a portion of the adhesive layer 24 atan interface between the adhesive layer 24 and the portion of the thinmetallic layer 25 that is irradiated and ablated. In other words, in thebonding structure 23 shown in FIG. 2, the portion of the thin metalliclayer 25 that is irradiated by the IR laser 14 is heated and vaporized,and this heating and ablation of the thin metallic layer 25 results inheating of the surrounding material of the adhesive layer 24 (at theinterface between the irradiated thin metallic layer 25 and adhesivelayer 24), which causes ablation of the adhesive layer. In addition,depending on the IR absorption properties of the material used to formthe adhesive layer 24, ablation of the adhesive layer 24 is furtherachieved by any additional heating that is due to absorption of the IRenergy by the adhesive layer 24.

In one embodiment of the invention, the thin metallic layer 25 is formedof a metallic material having properties such as being reactive (notinert), soft, and having a relatively low melting point. For example,the thin metallic layer 25 may be formed of materials such as aluminum(Al), tin (Sn) or zinc (Zn). Moreover, in one embodiment of theinvention, the thin metallic layer 25 is formed with a thickness in arange of about 5 nanometers to about 100 nanometers. The thin metalliclayer 25 is formed on the handler wafer 22 using one of various standardtechniques such as chemical vapor deposition (CVD), physical vapordeposition (PVD), or atomic layer deposition (ALD). The ablationthreshold of IR laser irradiation (level of exposure and time ofexposure) will vary depending on the thickness and type of metallicmaterial used to form the thin metallic layer 25. In all instances, thethin metallic layer 25 is configured to substantially absorb (and notreflect) the IR laser energy, so that ablation of the thin metalliclayer 25 occurs.

The adhesive layer 24 can be formed using known materials and depositiontechniques. For instance, the adhesive layer 24 can be formed of anysuitable polymeric adhesive material, and the adhesive material can bespin-coated either on the thin metal layer 25, or on a surface of the Sidevice wafer 21. Thereafter, a standard bonding process is implementedto bond the device and handler wafers 21 and 22.

FIG. 3 schematically depicts a stack structure comprising a bondingstructure for temporarily bonding a device wafer to a handler wafer,according to another embodiment of the invention. In particular, FIG. 3is a schematic side view of a stack structure 30 which is similar to thestack structure 20 of FIG. 2, except that a bonding structure 33 shownin FIG. 3 comprises a first adhesive layer 34, a second adhesive layer36, and a thin metallic layer 35 disposed between the first and secondadhesive layers 34, 36. In the embodiment of FIG. 3, the bondingstructure 33 further reduces an ablation threshold by having twometal-adhesive material interfaces which increases the IR absorption andheating of the bonding structure 33 and, thus, increases the efficiencyof the ablation process.

The first and second adhesive layers 34 and 36, and the thin metalliclayer 35 may be formed of the same or similar materials as discussedabove with reference to FIG. 2. In the embodiment of FIG. 3, the secondadhesive layer 36 can be spin-coated onto the surface of the handlerwafer 22 and then cured using a known curing process. The curing processresults in formation of a polymer passivation layer upon which the thinmetallic film 35 may be deposited using metallic materials and methodsas discussed above. The first adhesive layer 34 can be spin-coated ontothe thin metal layer 35 or onto the surface of the device wafer 21.Thereafter, the device and handler wafers 21 and 22 are bonded togetherusing known bonding techniques.

FIG. 4 schematically depicts a stack structure comprising a bondingstructure for temporarily bonding a device wafer to a handler wafer,according to another embodiment of the invention. In particular, FIG. 4is a schematic side view of a stack structure 40 which is similar to thestack structure 20 of FIG. 2, except that a bonding structure 43 shownin FIG. 4 comprises an adhesive layer 44 in contact with a thin metalliclayer 45 having a roughed, non-planar surface (as depictedillustratively, by the cross-hatching of the layer 45). The adhesivelayer 44 and the thin metallic layer 45 may be formed of the same orsimilar materials as discussed above with reference to FIG. 2.

In the embodiment of FIG. 4, the roughed surface topography of the thinmetallic layer 45 serves to increase the contact area of the interfacebetween the adhesive layer 44 and the thin metallic layer 45. Theincreased contact area reduces the ablation threshold by enabling moreheat transfer from the thin metal layer 45 to the surrounding materialof the adhesive layer 44 as the thin metallic layer 45 is heated andablated by IR irradiation. In one embodiment of the invention, the thinmetallic layer 45 with a rough surface topography can be formed by firstetching (dry etch or wet etch) the surface of the handler wafer 22 toroughen the silicon surface of the handler wafer 22. A metallic materialis then conformally deposited on the roughened surface of the Si waferhandler 22 (using suitable metallic materials and deposition methods asdiscussed above). This deposition process naturally forms arough-surface thin metallic material 45 as the deposition of themetallic material conformally follows the topography of the roughenedsurface of the handler wafer 22.

FIG. 5 schematically depicts a stack structure comprising a bondingstructure for temporarily bonding a device wafer to a handler wafer,according to another embodiment of the invention. In particular, FIG. 5is a schematic side view of a stack structure 50 which is similar to thestack structure 30 of FIG. 3, except that a bonding structure 53 shownin FIG. 5 comprises a rough surface thin metallic layer 55 disposedbetween a first adhesive layer 54 and a second adhesive layer 56. Theadhesive layers 54, 56 and the roughened surface thin metallic layer 55can be formed of the same or similar materials as discussed above. Inthe embodiment of FIG. 5, the roughened surface of the thin metalliclayer 55 serves to increase the contact area of the interface betweenthe first adhesive layer 54 and the thin metallic layer 55, as well asincrease the contact area of the interface between the second adhesivelayer 56 and the thin metallic layer 55. This bonding structure 53further reduces the ablation threshold by enabling more heat transferfrom the thin metal layer 55 to the surrounding materials of the firstand second adhesive layers 54, 56, thereby enhancing the ablationefficiency of the irradiated materials in the laser-ablated region 16.

The stack structure 50 of FIG. 5 can be fabricated by spin coating apolymeric adhesive material onto the handler wafer 22, followed by anadhesive cure process to form the second adhesive layer 56. The secondadhesive layer 56 is then etched using a dry etch process (e.g., plasmaetch) to roughen the surface topography of the adhesive layer 56. Ametallic material is then conformally deposited on the roughened surfaceof the first adhesive layer 56 (using suitable metallic materials anddeposition methods as discussed above). This deposition processnaturally forms a rough-surface thin metallic material 55 as thedeposition of the metallic material conformally follows the topographyof the roughened surface of the etched adhesive layer 56. The firstadhesive layer 54 can be spin-coated onto the thin metallic layer 55 oronto the surface of the device wafer 21 using known techniques, followedby a bonding process to bond the device and handler wafers 21 and 22together.

FIG. 6 schematically depicts a stack structure comprising a bondingstructure for temporarily bonding a device wafer to a handler wafer,according to another embodiment of the invention. More specifically,FIG. 6 is a schematic side view of a stack structure 60 comprising asilicon device wafer 21, a silicon handler wafer 22, and a bondingstructure 63. The bonding structure 63 comprises a protective metallayer 61 and an adhesive layer 64. In the embodiment of FIG. 6, theprotective metal layer 61 is disposed between the adhesive layer 64 (ofthe bonding structure 63) and the device wafer 21 to protect the devicewafer 21 from being irradiated with the infrared energy emitted from theIR laser 14 during a laser ablation process.

In the embodiment of FIG. 6, the protective metal layer 61 is configured(in material composition and thickness) to reflect incident IR laserenergy away from the device layer 21 back into the adhesive layer 64. Inthis embodiment, although a thin metallic layer is not used in thebonding structure 63 as a primary releasable layer for IR laserablation, the reflection of the IR laser energy from the protectivemetal layer 61 back into the adhesive layer 64 increases the IRabsorption (and thus heat generation) in the irradiated portion of theadhesive layer 64, which enhances the ablation efficiency of theirradiated adhesive material in the laser-ablated region 16. Theprotective metallic layer 61 may be formed using an inert metallicmaterial such as titanium, gold or copper, with a thickness that issufficient to reflect the IR energy (thicker than a skin depth of theprotective metal layer 61 at the given IR laser wavelength).

FIG. 7 schematically depicts a stack structure comprising a bondingstructure for temporarily bonding a device wafer to a handler wafer,according to another embodiment of the invention. More specifically,FIG. 7 is a schematic side view of a stack structure 70 which is similarto the stack structures 20 (of FIG. 2) and 60 (of FIG. 6,) wherein abonding structure 73 shown in FIG. 7 comprises a combination of aprotective metal layer 61, an adhesive layer 74 and a thin metalliclayer 75 that serves as the primary releasable layer for IR laserablation. The adhesive layer 74 and the thin metallic layer 75 may beformed of the same or similar materials as discussed above withreference to FIG. 2, and the protective metal layer 61 may be formed ofthe same materials discussed above with reference to FIG. 6. In theembodiment of FIG. 7, the ablation efficiency of the irradiated adhesivematerial and metallic layer 75 in the laser-ablated region 16 is furtherenhanced by the additional IR irradiation reflected back from theprotective metal layer 61.

FIG. 8 schematically depicts a stack structure comprising a bondingstructure for temporarily bonding a device wafer to a handler wafer,according to another embodiment of the invention. In particular, FIG. 8is a schematic side view of a stack structure 80 which is similar to thestack structure 20 of FIG. 2, except that a bonding structure 83 shownin FIG. 8 comprises an adhesive layer 84, and a thin metallic layer 85,wherein the adhesive layer 84 comprises infrared energy absorbingnanoparticles (schematically illustrated by the dotted fill of layer84). The IR energy absorbing nanoparticles enhances the IR energyabsorption of the adhesive layer 84 and, thus, reduces the overallablation threshold of the bonding structure 83.

In one embodiment of the invention, the adhesive layer 84 is formed of apolymer adhesive material that is premixed with metallic nanoparticlesthat improve the IR absorption of the adhesive material. For example,the nanoparticles may be formed of Sn, Zn, Al, carbon nanotubes orgraphene, or a combination thereof. The adhesive layer 84 may be formedby spin coating the polymer adhesive material with the premixed withmetallic nanoparticles onto the surface of the thin metallic layer 85 oronto the surface of the device wafer 21.

FIG. 9 schematically depicts a stack structure comprising a bondingstructure for temporarily bonding a device wafer to a handler wafer,according to another embodiment of the invention. In particular, FIG. 9is a schematic side view of a stack structure 90 which is similar to thestack structure 60 of FIG. 6, except that a bonding structure 93 shownin FIG. 9 comprises an adhesive layer 94 which comprises infrared energyabsorbing nanoparticles (schematically illustrated by the dotted fill oflayer 94), to enhance IR energy absorption of the adhesive layer 94 andreduce the ablation threshold of the bonding structure 93. Thereflection of the IR laser energy from the protective metal layer 61back into the nanoparticle adhesive layer 94 further increases the IRabsorption and heat generation in the irradiated portion of thenanoparticle adhesive layer 94 to thereby even further enhance theablation efficiency of the irradiated material in the laser-ablatedregion 16 of the bonding structure 93. The protective metal layer 61 andnanoparticle adhesive layer 94 may be formed of the same or similarmaterials discussed above.

In other embodiments of the invention, a bonding structure may include ananoparticle adhesive layer alone, with no laser-ablated thin metalliclayer or protective metal layer. In particular, a stack structure can beformed by bonding a silicon device wafer and a silicon handler wafertogether with an adhesive layer having infrared energy absorbingnanoparticles, wherein the adhesive layer serves as a releasable layerby infrared ablation of the adhesive layer. In other alternativeembodiments, the adhesive layers shown in FIGS. 3, 4, 5, and 7 can beformed with nanoparticle adhesive layers.

FIGS. 10A, 10B and 10C schematically depict an apparatus to perform adebonding process to separate a device wafer and handler wafer,according to an embodiment of the invention. In particular, FIGS. 10A,10B and 10C schematically illustrate an apparatus 100 for processing astack structure comprising a device wafer 21, a handler wafer 22, and abonding structure 123 disposed between the device wafer 21 and thehandler wafer 22. The bonding structure 123 may be any one of thebonding structure depicted in FIG. 2, 3, 4, 5, 6, 7, 8 or 9, forexample. The apparatus 100 comprises a vacuum system comprising a firstvacuum chuck 110 and a second vacuum chuck 120, as well as an infraredlaser scan system 115, 117. The vacuum system applies a vacuum suctionforce through the first vacuum chuck 110 to hold the stack structure21/123/22 in place with the device wafer 21 in contact with the firstvacuum chuck 110.

The infrared laser scan system 115,117 applies a pulsed infrared laser115 at the backside of the handler wafer 22 to irradiate the bondingstructure 123 with infrared energy and ablate the bonding structure 123to release the handler wafer from the device wafer. A scan system 117 isused to scan the IR laser 115 back and forth across the stack structure22/123/21, wherein the infrared laser scan system 115, 117 controls thelaser ablation scan process by controlling the power (energy densitybeam), the scan speed, and the pulse rate, for example, in a manner thatis sufficient to effectively ablate the bonding structure 123, or aportion of the bonding structure 123 at desired target regions of thestack structure. The parameters of the IR laser scan can vary dependingon the bonding structure framework.

FIG. 10B illustrates a state of the apparatus 100 in which the IR laserscan is complete and the entire bonding structure is sufficientlyablated to release the handler wafer 22 from the device wafer 21. Inparticular, FIG. 10B schematically illustrates a state in which acompletely ablated bonding structure 123A exists between the handlerwafer 22 and the device wafer 21 (as schematically illustrated bycross-hatching of the layer 123A shown in FIG. 10B). In otherembodiments of the invention, the IR laser scan process can becontrolled such as certain regions of the bonding structure are laserablated (e.g., diced die regions), while other regions of the bondingstructure are not.

After IR laser ablation of the bonding structure 123, referring to FIG.10C, the vacuum system places the second vacuum chuck 120 in contactwith the handler wafer 22, and applies a vacuum suction force throughthe second vacuum chuck 120, and the second vacuum chuck 120 is liftedup with a lifting device 122 to pull the handler wafer 22 from thedevice wafer 21.

Thereafter, the device wafer 21 can be transferred to a chemical stationto etch or otherwise remove the residual temporary adhesive layer 123Athat remains on the surface of the device wafer 21 after the debondingprocess shown in FIG. 10C. Although not shown in FIGS. 10A, 10B and 10C,the apparatus 100 may further comprise an air handler,filtration/condensation system or exhaust system to remove and trapdebris and exhaust excess gases that are generated during the debondingprocess. It is to be understood that FIGS. 10A, 10B and 10C genericallyillustrate a high-level structural depiction of a standardwafer-processing machine that can be implemented or retrofitted for IRlaser ablation and wafer debonding, as discussed herein.

Although embodiments have been described herein with reference to theaccompanying drawings for purposes of illustration, it is to beunderstood that the present invention is not limited to those preciseembodiments, and that various other changes and modifications may beaffected herein by one skilled in the art without departing from thescope of the invention.

1.˜11. (canceled)
 12. A stack structure, comprising: a device wafer; a silicon handler wafer; and a bonding structure disposed between the device wafer and the silicon handler wafer, wherein the bonding structure bonds the device and silicon handler wafers together, wherein the bonding structure comprises: an adhesive layer; and a metallic layer that is vaporizable by infrared ablation to serve as a releasable layer of the bonding structure by infrared exposure of the bonding structure through the silicon handler wafer, wherein the metallic layer has a thickness in a range of about 5 nanometers to less than 100 nanometers which is configured to be substantially or completely vaporized by infrared ablation to cause the release of the device wafer from the silicon handler wafer as a direct result of the infrared ablation of the metallic layer.
 13. The stack structure of claim 12, wherein the adhesive layer further serves as a releasable layer by infrared ablation of at least a portion of the adhesive layer at an interface between the adhesive layer and the metallic layer due, in part to, absorption of infrared energy by the metallic layer.
 14. The stack structure of claim 12, wherein the metallic layer is ablated by irradiation of infrared energy having a wavelength in a range of about 5 μm to about 30 μm.
 15. (canceled)
 16. The stack structure of claim 12, wherein the thin metallic layer is formed of at least one of Al, Sn, and Zn.
 17. The stack structure of claim 12, wherein the metallic layer is directly deposited on a surface of the silicon handler wafer.
 18. The stack structure of claim 12, wherein the metallic layer is formed with a rough surface to increase a contact area between the metallic layer and the adhesive layer.
 19. The stack structure of claim 12, wherein the adhesive layer comprise a first adhesive layer and a second adhesive layer, wherein the metallic layer is disposed between the first and second adhesive layers.
 20. The stack structure of claim 12, further comprising a protective metallic layer disposed between the releasable layer and the device wafer to protect the device wafer from being irradiated with the infrared energy.
 21. The stack structure of claim 20, wherein the protective metallic layer is formed of at least one of titanium, gold or copper.
 22. The stack structure of claim 12, wherein the adhesive layer comprises a polymer material having infrared energy absorbing nanoparticles.
 23. The stack structure of claim 22, wherein the nanoparticles are formed of at least one of Sn, Zn, Al, carbon nanotubes and graphene.
 24. The stack structure of claim 12, wherein the device wafer is a silicon wafer.
 25. A stack structure, comprising: a device wafer; a silicon handler wafer; and a bonding structure disposed between the device wafer and the silicon handler wafer, wherein the bonding structure bonds the device and silicon handler wafers together, wherein the bonding structure comprises an adhesive layer, wherein the adhesive layer comprises a layer of adhesive material comprising infrared energy absorbing nanoparticles that are vaporizable by infrared ablation so that the adhesive layer serves as a releasable layer by vaporization of the nanoparticles when infrared radiation is directed at the bonding structure through the silicon handler wafer, wherein the adhesive layer comprises a concentration of infrared energy absorbing nanoparticles which is configured to be substantially or completely vaporized by infrared ablation to cause release of the device wafer and the silicon handler wafer as a direct result of the infrared ablation of the infrared energy absorbing nanoparticles.
 26. The stack structure of claim 25, wherein the nanoparticles are formed of at least one of Sn, Zn, Al, carbon nanotubes and graphene.
 27. (canceled)
 28. (canceled)
 29. The stack structure of claim 25, further comprising a non-ablating protective metallic layer disposed between the bonding structure and the device wafer to protect the device wafer from being irradiated with the infrared energy and to reflect the infrared energy away from the device wafer. 